Olefin-based polymer, film prepared therefrom, and preparation methods therefor

ABSTRACT

The present invention relates to an olefin-based polymer, a film prepared therefrom, and preparation methods therefor. An olefin-based polymer according to an embodiment of the present invention has excellent processability, and a film prepared therefrom, particularly, a linear low density polyethylene film has excellent mechanical strength, in particular, drop impact strength.

TECHNICAL FIELD

The present invention relates to an olefin-based polymer, a filmprepared therefrom, and a method for preparing the same. Specifically,the present invention relates to an olefin-based polymer havingexcellent processability, an olefin-based polymer film which is preparedtherefrom and has excellent mechanical strength, in particular,excellent drop impact strength, and a method for preparing the same.

BACKGROUND ART

A metallocene catalyst which is one of the catalysts used in olefinpolymerization, which is a compound in which a ligand such ascyclopentadienyl, indenyl, or cycloheptadienyl is coordinated to atransition metal or a transition metal halogen compound, has a sandwichstructure as a basic form.

A Ziegler-Natta catalyst which is another catalyst used for polymerizingolefins has heterogeneous properties of an active site, since a metalcomponent as an active site is dispersed on an inert solid surface;however, the metallocene catalyst is known as a single-site catalysthaving identical polymerization properties in all active sites, since itis one compound having a certain structure. A polymer polymerized withthe metallocene catalyst as such has a narrow molecular weightdistribution, a uniform comonomer distribution, and copolymerizationactivity higher than the Ziegler Natta catalyst.

Meanwhile, a linear low-density polyethylene (LLDPE) is prepared bycopolymerizing ethylene and α-olefin at a low pressure using apolymerization catalyst, has a narrow molecular weight distribution anda short chain branch (SCB) having a certain length, and does not have along chain branch (LCB) in general. A film prepared with a linearlow-density polyethylene has high breaking strength and elongation, andexcellent tear strength, impact strength, and the like, together withgeneral properties of polyethylene, and thus, is widely used in astretch film, an overlap film, and the like to which it isconventionally difficult to apply low-density polyethylene orhigh-density polyethylene.

However, the linear low-density polyethylene prepared by a metallocenecatalyst has poor processability due to a narrow molecular weightdistribution, and a film prepared therefrom tends to have lowered heatseal properties.

Therefore, an olefin-based polymer which allows preparation of a filmhaving excellent mechanical strength, in particular, excellent dropimpact strength while having excellent processability, is beingdemanded.

DISCLOSURE Technical Problem

An object of the present invention is to provide an olefin-based polymerwhich allows preparation of an olefin-based polymer film havingexcellent mechanical strength, in particular, excellent drop impactstrength while having excellent processability.

Another object of the present invention is to provide an olefin-basedpolymer film which is prepared from the olefin-based polymer and hasexcellent mechanical strength, in particular, drop impact strength.

Another object of the present invention is to provide a method forpreparing the olefin-based polymer and the olefin-based polymer film.

Technical Solution

In one general aspect, an olefin-based polymer which has (1) a densityof 0.915 to 0.935 g/cm³, preferably 0.915 to 0.930 g/cm³; (2) a meltindex (I_(2.16)) of 0.3 to 3.0 g/10 min, preferably 0.5 to 2.0 g/10 minas measured with a load of 2.16 kg at 190° C.; (3) a ratio between amelt index (I_(21.6)) measured with a load of 21.6 kg and a melt index(I_(2.16)) measured with a load of 2.16 kg at 190° C. (melt flow ratio;MFR) of 20 to 50, preferably 20 to 45; and (4) a comonomer distributionslope (CDS) defined by the following Equation 1 of 3 or more, preferably3 to 15 is provided, wherein a film prepared therefrom has a drop impactstrength of 1,200 to 1,550 g based on a thickness of 50 μm:

$\begin{matrix}{{CDS} = \frac{{\log C_{80}} - {\log C_{20}}}{{\log M_{80}} - {\log M_{20}}}} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$

wherein C₂₀ and C₈₀ are comonomer contents at points where cumulativeweight fractions are 20% and 80%, respectively, in a comonomerdistribution, and M₂₀ and M₈₀ are molecular weights at points wherecumulative weight fractions are 20% and 80%, respectively, in acomonomer distribution.

In a specific example of the present invention, the olefin-based polymermay be prepared by polymerizing an olefin-based monomer in the presenceof a hybrid catalyst including: at least one first transition compoundrepresented by the following Chemical Formula 1; and at least one secondtransition metal compound selected from a compound represented by thefollowing Chemical Formula 2 and a compound represented by the followingChemical Formula 3:

-   -   wherein M₁ and M₂ are different from each other and        independently of each other titanium (Ti), zirconium (Zr), or        hafnium (Hf),    -   X is independently of each other halogen, C₁₋₂₀ alkyl, C₂₋₂₀        alkenyl, C₂₋₂₀ alkynyl, C₆₋₂₀ aryl, C₁₋₂₀ alkyl C₆₋₂₀ aryl,        C₆₋₂₀ aryl C₁₋₂₀ alkyl, C₁₋₂₀ alkylamido, or C₆₋₂₀ arylamido,        and

R₁ to R₁₀ are independently of one another hydrogen, substituted orunsubstituted C₁₋₂₀ alkyl, substituted or unsubstituted C₂₋₂₀ alkenyl,substituted or unsubstituted C₆-20 aryl, substituted or unsubstitutedC₁₋₂₀ alkyl C₆₋₂₀ aryl, substituted or unsubstituted C₆₋₂₀ aryl C₁₋₂₀alkyl, substituted or unsubstituted C₁₋₂₀ heteroalkyl, substituted orunsubstituted C₃₋₂₀ heteroaryl, substituted or unsubstituted C₁₋₂₀alkylamido, substituted or unsubstituted C₆₋₂₀ arylamido, substituted orunsubstituted C₁₋₂₀ alkylidene, or substituted or unsubstituted C₁₋₂₀silyl, but R₁ to R₁₀ may be independently of each other connected to anadjacent group to form a substituted or unsubstituted saturated orunsaturated C₄₋₂₀ ring.

In a specific example of the present invention, M₁ and M₂ may bedifferent from each other and be zirconium or hafnium, respectively, Xmay be halogen or C₁₋₂₀ alkyl, respectively, and R₁ to R₁₀ may behydrogen, substituted or unsubstituted C₁₋₂₀ alkyl, substituted orunsubstituted C₁₋₂₀ alkenyl, or substituted or unsubstituted C₆₋₂₀ aryl,respectively.

In a preferred specific example of the present invention, M₁ may behafnium, M₂ may be zirconium, and X may be chlorine or methyl.

In a preferred specific example of the present invention, the firsttransition metal compound may be at least one of transition metalcompounds represented by the following Chemical Formulae 1-1 and 1-2,and the second transition metal compound may be at least one oftransition metal compounds represented by the following ChemicalFormulae 2-1, 2-2, and 3-1:

wherein Me is a methyl group.

In a specific example of the present invention, a mole ratio of thefirst transition metal compound to the second transition metal compoundis in a range of 100:1 to 1:100.

In a specific example of the present invention, the catalyst may includeat least one cocatalyst selected from the group consisting of a compoundrepresented by the following Chemical Formula 4, a compound representedby the following Chemical Formula 5, and a compound represented by thefollowing Chemical Formula 6:

[L-H]⁺[Z(A)₄]⁻ or [L]⁺[Z(A)₄]⁻  [Chemical Formula 6]

-   -   wherein n is an integer of 2 or more, R_(a) is a halogen atom, a        C₁₋₂₀ hydrocarbon group, or a C₁₋₂₀ hydrocarbon group        substituted with halogen,    -   D is aluminum (Al) or boron (B), R_(b), R_(c), and R_(d) are        independently of one another a halogen atom, a C₁₋₂₀ hydrocarbon        group, a C₁₋₂₀ hydrocarbon group substituted with halogen, or a        C₁₋₂₀ alkoxy group,    -   L is a neutral or cationic Lewis base, [L-H]⁺ and [L]⁺ are a        Bronsted acid, Z is a group 13 element, and A is independently        of each other a substituted or unsubstituted C₆₋₂₀ aryl group or        a substituted or unsubstituted C₁₋₂₀ alkyl group.

In a specific example of the present invention, the catalyst may furtherinclude a carrier which supports a transition metal compound, acocatalyst compound, or both of them.

In a preferred specific example of the present invention, the carriermay include at least one selected from the group consisting of silica,alumina, and magnesia.

Here, a total amount of the hybrid transition metal compound supportedon the carrier may be 0.001 to 1 mmol based on 1 g of the carrier, and atotal amount of the cocatalyst compound supported on the carrier may be2 to 15 mmol based on 1 g of the carrier.

In a specific example of the present invention, the olefin-based polymermay be a copolymer of an olefin-based polymer and an olefin-basedcomonomer. Specifically, the olefin-based monomer may be ethylene, andthe olefin-based comonomer may be at least one selected from the groupconsisting of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene,1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene,1-tetradecene, and 1-hexadecene. Preferably, the olefin-based polymermay be a linear low-density polyethylene in which the olefin-basedpolymer is ethylene and the olefin-based monomer is 1-hexene.

In another general aspect, a method for preparing an olefin-basedpolymer includes: polymerizing an olefin-based monomer in the presenceof a hybrid catalyst including: at least one first transition metalcompound represented by Chemical Formula 1; and at least one secondtransition metal compound selected from the compound represented byChemical Formula 2 and the compound represented by Chemical Formula 3,thereby obtaining an olefin-based polymer, wherein the olefin-basedpolymer has (1) a density of 0.915 to 0.935 g/cm³, preferably 0.915 to0.930 g/cm³; (2) a melt index (I_(2.16)) of 0.3 to 3.0 g/10 min,preferably 0.5 to 2.0 g/10 min as measured with a load of 2.16 kg at190° C.; (3) a ratio between a melt index (I_(21.6)) measured with aload of 21.6 kg and a melt index (I_(2.16)) measured with a load of 2.16kg at 190° C. (melt flow ratio; MFR) of 20 to 50, preferably 20 to 45;and (4) a comonomer distribution slope (CDS) defined by Equation 1 of 3or more, preferably 3 to 15, and a film prepared therefrom has a dropimpact strength of 1,200 to 1,550 g based on a thickness of 50 μm.

In a specific example of the present invention, polymerization of theolefin-based monomer may be gas phase polymerization, specifically, thepolymerization of the olefin-based monomer may be performed in a gasphase fluidized bed reactor.

Advantageous Effects

An olefin-based polymer according to an embodiment of the presentinvention has excellent processability, and a film prepared therefrom,particularly, a linear low-density polyethylene film, has excellentmechanical strength, in particular, excellent drop impact strength.

DESCRIPTION OF DRAWINGS

FIG. 1 is a GPC-FTIR graph for describing a method for measuring a CDSdefined by Equation 1.

FIGS. 2 to 6 are GPC-FTIR graphs for measuring a CDS of olefin-basedpolymers of Examples 1 to 5, respectively.

FIGS. 7 and 8 are GPC-FTIR graphs for measuring a CDS of olefin-basedpolymers of Comparative Examples, respectively.

BEST MODE

Hereinafter, the present invention will be described in more detail.

Olefin-Based Polymer

According to an embodiment of the present invention, an olefin-basedpolymer having (1) a density of 0.915 to 0.935 g/cm³; (2) a melt index(I_(2.16)) of 0.3 to 3.0 g/10 min as measured with a load of 2.16 kg at190° C.; (3) a ratio between a melt index (I_(21.6)) measured with aload of 21.6 kg and a melt index (I_(2.16)) measured with a load of 2.16kg at 190° C. (melt flow ratio; MFR) of 20 to 50; and (4) a comonomerdistribution slope (CDS) defined by the following Equation 1 of 3 ormore is provided, wherein a film prepared therefrom has a drop impactstrength of 1,200 to 1,550 g based on a thickness of 50.

In a specific example of the present invention, the olefin-based polymerhas a density of 0.915 to 0.935 g/cm³. Preferably, the olefin-basedpolymer may have a density of 0.915 to 0.930 g/cm³.

In a specific example of the present invention, the olefin-based polymermay have a melt index (I_(2.16)) of 0.3 to 3.0 g/10 min as measured witha load of 2.16 kg at 190° C. Preferably, the olefin-based polymer mayhave a melt index of 0.5 to 2.0 g/10 min as measured with a load of 2.16kg at 190° C.

In a specific example of the present invention, the olefin-based polymermay have a ratio between a melt index (I_(21.6)) measured with a load of21.6 kg and a melt index (I_(2.16)) measured with a load of 2.16 kg at190° C. (melt flow ratio; MFR) of 20 to 50. Preferably, the olefin-basedpolymer may have MFR of 20 to 45.

In a specific example of the present invention, the olefin-based polymermay have a comonomer distribution slope (CDS) defined by the followingEquation 1 of 3 or more. Preferably, the olefin-based polymer may havethe CDS of 3 to 15.

$\begin{matrix}{{CDS} = \frac{{\log C_{80}} - {\log C_{20}}}{{\log M_{80}} - {\log M_{20}}}} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$

-   -   wherein C₂₀ and C₈₀ are comonomer contents at points where        cumulative weight fractions are 20% and 80%, respectively, in a        comonomer distribution, and M₂₀ and M₈₀ are molecular weights at        points where cumulative weight fractions are 20% and 80%,        respectively, in a comonomer distribution.

The CDS of the olefin-based polymer represents a slope of a comonomercontent to a molecular weight at points where cumulative weightfractions are 20% and 80%, respectively, in a comonomer distributiongraph. As the CDS of the olefin-based polymer is higher, a copolymer isconcentrated on a polymer chain having a higher molecular weight, sothat mechanical strength and heat seal properties may be excellent.

Here, the comonomer distribution of the olefin-based polymer may becontinuously measured with the molecular weight and the molecular weightdistribution of the polymer, using GPC-FTIR equipment.

In a specific example of the present invention, a film prepared from theolefin-based polymer has a drop impact strength of 1,200 to 1,550 gbased on a thickness of 50 μm. Preferably, the film prepared from theolefin-based polymer may have a drop impact strength of 1,250 to 1,550 gbased on a thickness of 50 μm.

It is understood that since the olefin-based polymer according to anembodiment of the present invention has a relatively large molecularweight distribution and there are more short chain branches in a highmolecular weight component, the mechanical strength, in particular, thedrop impact strength of the olefin-based polymer film prepared therefromare excellent.

In a specific example of the present invention, the olefin-based polymerfilm may be effectively used as a stretch film, an overlap film, alaminated film, a silage warp, an agricultural film, and the like.

In the specific example of the present invention, a method for molding afilm from the olefin-based polymer according to an embodiment of thepresent invention is not particularly limited, and may use a moldingmethod known in the art to which the present invention belongs. Forexample, the olefin-based polymer described above may be processed by acommon method such as blown film molding, extrusion molding, or castingmolding, thereby preparing an olefin-based polymer film. Among them,blown film molding is most preferred.

In a specific example of the present invention, the olefin-based polymermay be prepared by polymerizing an olefin-based monomer in the presenceof a hybrid catalyst including: at least one first transition compoundrepresented by the following Chemical Formula 1; and at least one secondtransition metal compound selected from a compound represented by thefollowing Chemical Formula 2 and a compound represented by the followingChemical Formula 3:

In Chemical Formulae 1 to 3, M₁ and M₂ are different from each other andindependently of each other titanium (Ti), zirconium (Zr), or hafnium(Hf). Specifically, M₁ and M₂ may be different from each other and bezirconium or hafnium, respectively. Preferably, M₁ may be hafnium and M₂may be zirconium.

X is independently of each other halogen, C₁₋₂₀ alkyl, C₂₋₂₀ alkenyl,C₂₋₂₀ alkynyl, C₆₋₂₀ aryl, C₁₋₂₀ alkyl C₆₋₂₀ aryl, C₆₋₂₀ aryl C₁₋₂₀alkyl, C₁₋₂₀ alkylamido, or C₆₋₂₀ arylamido. Specifically, X may behalogen or C₁₋₂₀ alkyl, respectively. Preferably, X may be chlorine ormethyl.

R₁ to R₁₀ are independently of one another hydrogen, substituted orunsubstituted C₁₋₂₀ alkyl, substituted or unsubstituted C₂₋₂₀ alkenyl,substituted or unsubstituted C₆₋₂₀ aryl, substituted or unsubstitutedC₁₋₂₀ alkyl C₆₋₂₀ aryl, substituted or unsubstituted C₆₋₂₀ aryl C₁₋₂₀alkyl, substituted or unsubstituted C₁₋₂₀ heteroalkyl, substituted orunsubstituted C₃₋₂₀ heteroaryl, substituted or unsubstituted C₁₋₂₀alkylamido, substituted or unsubstituted C₆₋₂₀ arylamido, substituted orunsubstituted C₁₋₂₀ alkylidene, or substituted or unsubstituted C₁₋₂₀silyl, in which R₁ to R₁₀ may be independently of each other connectedto an adjacent group to form a substituted or unsubstituted saturated orunsaturated C₄-20 ring. Specifically, R₁ to R₁₀ may be hydrogen,substituted or unsubstituted C₁₋₂₀ alkyl, substituted or unsubstitutedC₁₋₂₀ alkenyl, or substituted or unsubstituted C₆₋₂₀ aryl, respectively.

In a specific example of the present invention, M₁ and M₂ may bedifferent from each other and be zirconium or hafnium, respectively, Xmay be halogen or C₁₋₂₀ alkyl, respectively, and R₁ to R₁₀ may behydrogen, substituted or unsubstituted C₁₋₂₀ alkyl, substituted orunsubstituted C₁₋₂₀ alkenyl, or substituted or unsubstituted C₆₋₂₀ aryl,respectively.

In a preferred specific example of the present invention, M₁ may behafnium, M₂ may be zirconium, and X may be chlorine or methyl.

In a preferred specific example of the present invention, the firsttransition metal compound may be at least one of transition metalcompounds represented by the following Chemical Formulae 1-1 and 1-2,and the second transition metal compound may be at least one oftransition metal compounds represented by the following ChemicalFormulae 2-1, 2-2, and 3-1:

-   -   wherein Me is a methyl group.

In a specific example of the present invention, a mole ratio of thefirst transition metal compound to the second transition metal compoundis in a range of 100:1 to 1:100. Preferably, a mole ratio of the firsttransition metal compound to the second transition metal compound is ina range of 50:1 to 1:50. Preferably, a mole ratio of the firsttransition metal compound to the second transition metal compound is ina range of 10:1 to 1:10.

In a specific example of the present invention, the catalyst may includeat least one cocatalyst compound selected from the group consisting of acompound represented by the following Chemical Formula 4, a compoundrepresented by the following Chemical Formula 5, and a compoundrepresented by the following Chemical Formula 6:

wherein n is an integer of 2 or more, R_(a) is a halogen atom, C₁₋₂₀hydrocarbon, or C₁₋₂₀ hydrocarbon substituted with halogen.Specifically, R^(a) may be methyl, ethyl, n-butyl, or isobutyl.

-   -   wherein D is aluminum (Al) or boron (B), and R_(b), R_(c), and        R_(d) are independently of one another a halogen atom, a C₁₋₂₀        hydrocarbon group, a C₁₋₂₀ hydrocarbon group substituted with        halogen, or a C₁₋₂₀ alkoxy group. Specifically, when D is        aluminum (Al), R_(b), R_(c), and R_(d) may be independently of        one another methyl or isobutyl, and when D is boron (B), R_(b),        R_(c), and R_(d) may be pentafluorophenyl, respectively.

[L-H]⁺[Z(A)₄]⁻ or [L]⁺[Z(A)₄]⁻  [Chemical Formula 6]

wherein L is a neutral or cationic Lewis base, [L-H]⁺ and [L]⁺ are aBronsted acid, Z is a group 13 element, and A is independently of eachother a substituted or unsubstituted C₆₋₂₀ aryl group or a substitutedor unsubstituted C₁₋₂₀ alkyl group. Specifically, [L-H]+ may bedimethylanilinium cation, [Z(A)₄]⁻ may be [B(C₆F₅)₄]⁻, and [L]⁺ may be[(C₆H₅)₃C]⁺.

Specifically, an example of the compound represented by Chemical Formula4 includes methylaluminoxane, ethylaluminoxane, isobutylaluminoxane,butylaluminoxane, and the like, and is preferably methylaluminoxane, butis not limited thereto.

An example of the compound represented by Chemical Formula 5 includestrimethylaluminum, triethylaluminum, triisobutylaluminum,tripropylaluminum, tributylaluminum, dimethylchloroaluminum,triisopropylaluminum, tri-s-butylaluminum, tricyclopentylaluminum,tripentylaluminum, triisopentylaluminum, trihexylaluminum,trioctylaluminum, ethyldimethylaluminum, methyldiethylaluminum,triphenylaluminum, tri-p-tolylaluminum, dimethylaluminummethoxide,dimethylaluminumethoxide, trimethylboron, triethylboron,triisobutylboron, tripropylboron, tributylboron, and the like, and ispreferably trimethylaluminum, triethylaluminum, and triisobutylaluminum,but is not limited thereto.

An example of the compound represented by Chemical Formula 6 includestriethylammoniumtetraphenylboron, tributylammoniumtetraphenylboron,trimethylammoniumtetraphenylboron, tripropylammoniumtetraphenylboron,trimethylammoniumtetra(p-tolyl)boron,trimethylammoniumtetra(o,p-dimethylphenyl)boron,tributylammoniumtetra(p-trifluoromethylphenyl)boron,trimethylammoniumtetra(p-trifluoromethylphenyl)boron,tributylammoniumtetrapentafluorophenylboron,N,N-diethylaniliniumtetraphenylboron,N,N-diethylaniliniumtetrapentafluorophenylboron,diethylammoniumtetrapentafluorophenylboron,triphenylphosphoniumtetraphenylboron,trimethylphosphoniumtetraphenylboron,triethylammoniumtetraphenylaluminum,tributylammoniumtetraphenylaluminum,trimethylammoniumtetraphenylaluminum,tripropylammoniumtetraphenylaluminum,trimethylammoniumtetra(p-tolyl)aluminum,tripropylammoniumtetra(p-tolyl)aluminum,triethylammoniumtetra(o,p-dimethylphenyl)aluminum,tributylammoniumtetra(p-trifluoromethylphenyl)aluminum,trimethylammoniumtetra(p-trifluoromethylphenyl)aluminum,tributylammoniumtetrapentafluorophenylaluminum,N,N-diethylaniliniumtetraphenylaluminum,N,N-diethylaniliniumtetrapentafluorophenylaluminum,diethylammoniumtetrapentatetraphenylaluminum,triphenylphosphoniumtetraphenylaluminum,trimethylphosphoniumtetraphenylaluminum,tripropylammoniumtetra(p-tolyl)boron,triethylammoniumtetra(o,p-dimethylphenyl)boron,tributylammoniumtetra(p-trifluoromethylphenyl)boron,triphenylcarboniumtetra(p-trifluoromethylphenyl)boron,triphenylcarboniumtetrapentafluorophenylboron, and the like.

In a specific example of the present invention, the catalyst may furtherinclude a carrier which supports a transition metal compound, acocatalyst compound, or both of them. Specifically, the carrier maysupport both the transition metal compound and the cocatalyst compound.

Here, the carrier may include a material containing a hydroxyl group onthe surface, and preferably, may use a material having highly reactivehydroxyl group and siloxane group which is dried to remove moisture fromthe surface. For example, the carrier may include at least one selectedfrom the group consisting of silica, alumina, and magnesia.Specifically, silica, silica-alumina, silica-magnesia, and the likewhich are dried at a high temperature may be used as the carrier, andthese may usually contain oxide, carbonate, sulfate, and nitratecomponents such as Na₂O, K₂CO₃, BaSO₄, and Mg (NO₃)₂. In addition, thesemay include carbon, zeolite, magnesium chloride, and the like. However,the carrier is not limited thereto, and is not particularly limited aslong as it may support a transition metal compound and a cocatalystcompound.

The carrier may have an average particle size of 10 to 250 μm,preferably 10 to 150 μm, and more preferably 20 to 100 μm.

The carrier may have a micropore volume of 0.1 to 10 cc/g, preferably0.5 to 5 cc/g, and more preferably 1.0 to 3.0 cc/g.

The carrier may have a specific surface area of 1 to 1,000 m²/g,preferably 100 to 800 m²/g, and more preferably 200 to 600 m²/g.

In a preferred specific example of the present invention, the carriermay be silica. Here, a drying temperature of the silica may be 200 to900° C. The drying temperature may be 300 to 800° C., and morepreferably 400 to 700° C. When the drying temperature is lower than 200°C., silica has too much moisture so that the moisture on the surfacereacts with the cocatalyst compound, and when the drying temperature ishigher than 900° C., the structure of the carrier may collapse.

A concentration of a hydroxyl group in dried silica may be 0.1 to 5mmol/g, preferably 0.7 to 4 mmol/g, and more preferably 1.0 to 2 mmol/g.When the concentration of the hydroxyl group is less than 0.1 mmol/g,the supported amount of a first cocatalyst compound is lowered, and whenthe concentration is more than 5 mmol/g, the catalyst component becomesinactive.

The total amount of the transition metal compound supported on thecarrier may be 0.001 to 1 mmol based on 1 g of the carrier. When a ratiobetween the transition metal compound and the carrier satisfies theabove range, appropriate supported catalyst activity is shown, which isadvantageous in terms of the activity maintenance of a catalyst andeconomic feasibility.

The total amount of the cocatalyst compound supported on the carrier maybe 2 to 15 mmol based on 1 g of the carrier. When the ratio of thecocatalyst compound and the carrier satisfies the above range, it isadvantageous in terms of the activity maintenance of a catalyst andeconomic feasibility.

The carrier may be one or two or more. For example, both the transitionmetal compound and the cocatalyst compound may be supported on onecarrier, and each of the transition metal compound and the cocatalystcompound may be supported on two or more carriers. In addition, only oneof the transition metal compound and the cocatalyst compound may besupported on the carrier.

As a method for supporting the transition metal compound and/or thecocatalyst compound which may be used in the catalyst for olefinpolymerization, a physical adsorption method or a chemical adsorptionmethod may be used.

For example, the physical adsorption method may be a method of bringinga solution in which a transition metal compound is dissolved intocontact with a carrier and then drying, a method of bringing a solutionin which a transition metal compound and a cocatalyst compound aredissolved into contact with a carrier and then drying, a method ofbringing a solution in which a transition metal compound is dissolvedinto contact with a carrier and then drying to prepare a carrier onwhich the transition metal compound is supported, separately bringing asolution in which a cocatalyst compound is dissolved into contact with acarrier and then drying to prepare a carrier on which the cocatalystcompound is supported, and then mixing them, or the like.

The chemical adsorption method may be a method of first supporting acocatalyst compound on the surface of a carrier and then supporting atransition metal compound on the cocatalyst compound, a method ofbinding a functional group (for example, a hydroxyl group (—OH) on thesurface of silica, in the case of silica) on the surface of a carrierand a catalyst compound covalently.

In a specific example of the present invention, the olefin-based polymermay be a homopolymer of an olefin-based monomer or a copolymer ofolefin-based monomer and comonomer. Preferably, the olefin-based polymeris a copolymer of an olefin-based monomer and an olefin-based comonomer.

Here, the olefin-based monomer may be at least one selected from thegroup consisting of C₂₋₂₀ α-olefin, C₁₋₂₀ diolefin, C₃-20 cycloolefin,and C₃-20 cyclodiolefin.

For example, the olefin-based monomer may be ethylene, propylene,1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene,1-decene, 1-undecene, 1-dodecene, 1-tetradecene, or 1-hexadecene, andthe olefin-based polymer may be a homopolymer including only one or acopolymer including two or more of the olefin-based monomers exemplifiedabove.

In an exemplary embodiment, the olefin-based polymer may be a copolymerof ethylene and C₃-20 α-olefin. Preferably, the olefin-based polymer maybe a linear low-density polyethylene in which the olefin-based monomeris ethylene and the olefin-based comonomer is 1-hexene.

In this case, the content of ethylene is preferably 55 to 99.9 wt %, andmore preferably 90 to 99.9 wt %. The content of the α-olefin-basedcomonomer is preferably 0.1 to 45 wt %, and more preferably 0.1 to 10 wt%.

Method for Preparing Olefin-Based Polymer

According to an embodiment of the present invention, a method forpreparing an olefin-based polymer including: obtaining an olefin-basedpolymer by polymerizing an olefin-based monomer in the presence of ahybrid catalyst including: at least one first transition compoundrepresented by the following Chemical Formula 1; and at least one secondtransition metal compound selected from a compound represented by thefollowing Chemical Formula 2 and a compound represented by the followingChemical Formula 3, is provided:

-   -   wherein M₁, M₂, X, and R₁ to R₁₀ are as defined above in the        item of “olefin-based polymer”.

As described above, the olefin-based polymer prepared by the preparationmethod according to an embodiment of the present invention has: (1) adensity of 0.915 to 0.935 g/cm³, preferably 0.915 to 0.930 g/cm³; (2) amelt index (I_(2.16)) of 0.3 to 3.0 g/10 min, preferably 0.5 to 2.0 g/10min as measured with a load of 2.16 kg at 190° C.; (3) a ratio between amelt index (I_(21.6)) measured with a load of 21.6 kg and a melt index(I_(2.16)) measured with a load of 2.16 kg at 190° C. (melt flow ratio;MFR) of 20 to 50, preferably 20 to 45; and (4) a comonomer distributionslope (CDS) defined by the following Equation 1 of 3 or more, preferably3 to 15, wherein a film prepared therefrom has a drop impact strength of1,200 to 1,550 g based on a thickness of 50 μm:

$\begin{matrix}{{CDS} = \frac{{\log C_{80}} - {\log C_{20}}}{{\log M_{80}} - {\log M_{20}}}} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$

-   -   wherein C₂O, C₈₀, M₂₀, and M₈₀ are as defined above in the item        of “olefin-based polymer”.

In a specific example of the present invention, the olefin-based polymermay be polymerized by a polymerization reaction such as free radical,cationic, coordination, condensation, and addition polymerization, butis not limited thereto.

In an exemplary embodiment of the present invention, the olefin-basedpolymer may be prepared by a gas phase polymerization method, a solutionpolymerization method, a slurry polymerization method, or the like.Preferably, the polymerization of the olefin-based monomer may be gasphase polymerization, specifically, the polymerization of theolefin-based monomer may be performed in a gas phase fluidized bedreactor.

When the olefin-based polymer is prepared by a solution polymerizationmethod or a slurry polymerization method, an example of the solvent tobe used may include a C₅₋₁₂ aliphatic hydrocarbon solvent such aspentane, hexane, heptane, nonane, decane, and isomers thereof; anaromatic hydrocarbon solvent such as toluene and benzene; a hydrocarbonsolvent substituted with a chlorine atom such as dichloromethane andchlorobenzene; and a mixture thereof, but is not limited thereto.

BEST MODE FOR CARRYING OUT THE INVENTION Examples

Hereinafter, the present invention will be specifically describedthrough the following examples. However, the following examples are onlyillustrative of the present invention, and do not limit the scope of thepresent invention.

Preparation Example

The transition metal compound of Chemical Formula 1-1(bis(n-propylcyclopentadienyl) hafnium dichloride) and the transitionmetal compound of Chemical Formula 2-1 (bis(n-butylcyclopentadienyl)zirconium dichloride) were purchased from TCI, the transition metalcompound of Chemical Formula 1-2 (dimethylbis(n-propylcyclopentadienyl)hafnium dichloride), the transition metal compound of Chemical Formula2-2 (bis(i-butylcyclopentadienyl) zirconium dichloride), and thetransition metal compound of Chemical Formula 3-1((pentamethylcyclopentadienyl) (n-propylcyclopentadienyl) zirconiumdichloride) were purchased from MCN, and these were used without anadditional purification process.

Preparation Example 1

892 g of a 10% toluene solution of methylaluminoxane was added to 4.47 gof the transition metal compound of Chemical Formula 1-1 and 1.67 g ofthe transition metal compound of Chemical Formula 2-1, and the solutionwas stirred at room temperature for 1 hour. The solution after thereaction was added to 200 g of silica (XPO-2402), 1.5 L of toluene wasfurther added, and stirring was performed at 70° C. for 2 hours. Thesupported catalyst was washed with 500 mL of toluene, and was driedovernight at 60° C. under vacuum to obtain 280 g of a supported catalystin powder form.

Preparation Example 2

278 g of a supported catalyst was obtained in the same manner as inPreparation Example 1, except that 4.47 g of the transition metalcompound of Chemical Formula 1-1 and 1.67 g of the transition metalcompound of Chemical Formula 2-2 were used.

Preparation Example 3

280 g of a supported catalyst was obtained in the same manner as inPreparation Example 1, except that 4.47 g of the transition metalcompound of Chemical Formula 1-1 and 1.68 g of the transition metalcompound of Chemical Formula 3-1 were used.

Preparation Example 4

275 g of a supported catalyst was obtained in the same manner as inPreparation Example 1, except that 4.07 g of the transition metalcompound of Chemical Formula 1-2 and 1.67 g of the transition metalcompound of Chemical Formula 2-2 were used.

Preparation Example 5

278 g of a supported catalyst was obtained in the same manner as inPreparation Example 1, except that 4.07 g of the transition metalcompound of Chemical Formula 1-2 and 1.68 g of the transition metalcompound of Chemical Formula 3-1 were used.

Examples 1 to 5

Ethylene/1-hexene copolymers were prepared in the presence of thesupported catalysts, which were obtained in Preparation Examples 1 to 5,respectively, using a gas phase fluidized bed reactor. The ethylenepartial pressure of the reactor was maintained at about 15 kg/cm 2, andthe polymerization temperature was maintained at 80 to 90° C.

The polymerization conditions of the examples are shown in the followingTable 1.

TABLE 1 Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5Catalyst Prepa- Prepa- Prepa- Prepa- Prepa- ration ration ration rationration Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5Polymerization 85.2 82.1 83.9 83.4 84.4 temperature (° C.) Catalystinjection 1.87 2.25 1.5 1.21 1.18 amount (g/h) Hydrogen injection 1.120.85 2.53 0.57 2.35 amount (g/h) 1-Hexene injection 1.57 1.55 1.54 1.331.64 amount (kg/h) Hydrogen/ethylene 0.03 0.03 0.05 0.03 0.05concentration (%) ratio 1-Hexene/ethylene 1.32 1.23 1.37 1.17 1.47concentration (%) ratio Production amount 6.45 7.14 5.67 6.19 5.63 perhour (kg/h) Catalyst injection 85.2 82.1 83.9 83.4 84.4 amount (g/h)

Comparative Examples 1 and 2

For comparison, linear low-density polyethylenes M1810HN (density:0.9180 g/cm³, melt index: 1.0 g/10 min; Comparative Example 1) andM2010EN (density: 0.9200 g/cm³, melt index: 1.0 g/10 min; ComparativeExample 2) from Hanwha Solutions were used.

Test Example

The physical properties of the olefin-based polymer of the aboveexamples were measured by the following methods and criteria. Theresults are shown in Table 2.

(1) Density

Measured according to ASTM D 1505.

(2) Melt Index and Melt Index Ratio (MFR)

The melt index was measured with a load of 21.6 kg and a load of 2.16kg, respectively, at 190° C. in accordance with ASTM D1238, and theratio (MI_(21.6)/MI_(2.16)) was calculated.

(3) Comonomer Distribution Slope (CDS)

Measured at 170° C. using gel permeation chromatography-FTIR (GPC-FTIR).

TABLE 2 Example Example Example Example Example Comparative ComparativeUnit 1 2 3 4 5 Example 1 Example 2 Density g/cm³ 0.9188 0.9191 0.91910.9186 0.9197 0.9202 0.9178 Melt g/10 1.21 0.91 0.91 1.04 0.99 1.08 1.00index min MFR — 20.1 21.0 21.0 20.1 22.0 16.11 33.24 MW g/mol 200,363198,243 198,243 199,661 199,178 200,729 169,034 Mw/Mn — 1.88 2.2 2.22.07 2.23 2.12 2.52 CDS — 5.04 5.57 9.05 3.64 11.3 1.26 0.211

The resins of Examples 1 to 5 and Comparative Examples 1 and 2 wereprepared into films having a thickness of 50 μm, respectively, through a40 mm blown film extruder (40 mm 0 screw, 75 mm 0 die, 2 mm die gap).Here, the extrusion conditions were set toC₁/C₂/C₃/A/D1/D2=160/165/170/175/180/180° C., a screw speed of 60 rpm,and a blow-up ratio (BUR) of 2.

The physical properties of the olefin-based polymer films of theexamples and the comparative examples were measured by the followingmethods and criteria. The results are shown in Table 3.

(4) Drop Impact Strength

The drop impact strength was measured in accordance with the method ofASTM D1709 (A) in which a film having a thickness of 50 μm is fixed, anda weight having a diameter of 38.10±0.13 mm is dropped from a height of0.66±0.01 m.

(5) Haze

The film was molded into a standard of a thickness of 50 μm and the hazewas measured in accordance with ASTM D 1003. At this time, themeasurement was performed five times per one specimen, and their averagevalue was taken.

TABLE 3 Example Example Example Example Example Comparative ComparativeUnit 1 2 3 4 5 Example 1 Example 2 Drop g 1,300 1,390 1,390 1,495 1,4401,015 650 impact strength Haze % 5.43 5.99 5.99 5.99 7.18 8.72 4.66

INDUSTRIAL APPLICABILITY

The olefin-based polymer according to the specific example of thepresent invention has excellent processability, and the olefin-basedpolymer film prepared therefrom, specifically a linear low-densitypolyethylene film, has excellent mechanical strength, in particular,excellent drop impact strength.

1. An olefin-based polymer which has (1) a density of 0.915 to 0.935g/cm³; (2) a melt index (I_(2.16)) of 0.3 to 3.0 g/10 min as measuredwith a load of 2.16 kg at 190° C.; (3) a ratio between a melt index(I_(21.6)) measured with a load of 21.6 kg and a melt index (I_(2.16))measured with a load of 2.16 kg at 190° C. (melt flow ratio; MFR) of 20to 50; and (4) a comonomer distribution slope (CDS) defined by thefollowing Equation 1 of 3 or more, wherein a film prepared therefrom hasa drop impact strength of 1,200 to 1,550 g based on a thickness of 50μm: $\begin{matrix}{{CDS} = \frac{{\log C_{80}} - {\log C_{20}}}{{\log M_{80}} - {\log M_{20}}}} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$ wherein C₂₀ and C₈₀ are comonomer contents at points wherecumulative weight fractions are 20% and 80%, respectively, in acomonomer distribution, and M₂₀ and M₈₀ are molecular weights at pointswhere cumulative weight fractions are 20% and 80%, respectively, in acomonomer distribution.
 2. The olefin-based polymer of claim 1, whereinthe olefin-based polymer has (1) the density of 0.915 to 0.930 g/cm³;(2) the melt index of 0.5 to 2.0 g/10 min as measured with a load of2.16 kg at 190° C.; (3) the MFR of 20 to 45; and (4) the CDS of 3 to 15.3. The olefin-based polymer of claim 1, wherein the olefin-based polymeris prepared by polymerizing an olefin-based monomer in the presence of ahybrid catalyst including: at least one first transition compoundrepresented by the following Chemical Formula 1; and at least one secondtransition metal compound selected from a compound represented by thefollowing Chemical Formula 2 and a compound represented by the followingChemical Formula 3:

wherein M₁ and M₂ are different from each other and independently ofeach other titanium (Ti), zirconium (Zr), or hafnium (Hf), X isindependently of each other halogen, C₁₋₂₀ alkyl, C₂₋₂₀ alkenyl, C₂₋₂₀alkynyl, C₆₋₂₀ aryl, C₁₋₂₀ alkyl C₆₋₂₀ aryl, C₆₋₂₀ aryl C₁₋₂₀ alkyl,C₁₋₂₀ alkylamido, or C₆₋₂₀ arylamido, and R₁ to R₁₀ are independently ofone another hydrogen, substituted or unsubstituted C₁₋₂₀ alkyl,substituted or unsubstituted C₂₋₂₀ alkenyl, substituted or unsubstitutedC₆₋₂₀ aryl, substituted or unsubstituted C₁₋₂₀ alkyl C₆₋₂₀ aryl,substituted or unsubstituted C₆₋₂₀ aryl C₁₋₂₀ alkyl, substituted orunsubstituted C₁₋₂₀ heteroalkyl, substituted or unsubstituted C₃₋₂₀heteroaryl, substituted or unsubstituted C₁₋₂₀ alkylamido, substitutedor unsubstituted C₆₋₂₀ arylamido, substituted or unsubstituted C₁₋₂₀alkylidene, or substituted or unsubstituted C₁₋₂₀ silyl, but R₁ to R₁₀may be independently of each other connected to an adjacent group toform a substituted or unsubstituted saturated or unsaturated C₄₋₂₀ ring.4. The olefin-based polymer of claim 3, wherein M₁ and M₂ are differentfrom each other and are zirconium or hafnium, X is halogen or C₁₋₂₀alkyl, respectively, and R₁ to R₁₀ are hydrogen, substituted orunsubstituted C₁₋₂₀ alkyl, substituted or unsubstituted C₁₋₂₀ alkenyl,or substituted or unsubstituted C₆₋₂₀ aryl, respectively.
 5. Theolefin-based polymer of claim 4, wherein M₁ is hafnium, M₂ is zirconium,and X is chlorine or methyl.
 6. The olefin-based polymer of claim 3,wherein the first transition metal compound is at least one oftransition metal compounds represented by the following ChemicalFormulae 1-1 and 1-2, and the second transition metal compound is atleast one of transition metal compounds represented by the followingChemical Formulae 2-1, 2-2, and 3-1:

wherein Me is a methyl group.
 7. The olefin-based polymer of claim 3,wherein a mole ratio of the first transition metal compound to thesecond transition metal compound is in a range of 100:1 to 1:100.
 8. Theolefin-based polymer of claim 3, wherein the catalyst includes at leastone cocatalyst compound selected from the group consisting of a compoundrepresented by the following Chemical Formula 4, a compound representedby the following Chemical Formula 5, and a compound represented by thefollowing Chemical Formula 6:

wherein n is an integer of 2 or more, R_(a) is a halogen atom, a C₁₋₂₀hydrocarbon group, or a C₁₋₂₀ hydrocarbon group substituted withhalogen, D is aluminum (Al) or boron (B), R_(b), R_(c), and R_(d) areindependently of one another a halogen atom, a C₁₋₂₀ hydrocarbon group,a C₁₋₂₀ hydrocarbon group substituted with halogen, or a C₁₋₂₀ alkoxygroup, L is a neutral or cationic Lewis base, [L−H]⁺ and [L]⁺ are aBronsted acid, Z is a group 13 element, and A is independently of eachother a substituted or unsubstituted C₆₋₂₀ aryl group or a substitutedor unsubstituted C₁₋₂₀ alkyl group.
 9. The olefin-based polymer of claim8, wherein the catalyst further includes a carrier which supports thetransition metal compound, the cocatalyst compound, or both of them. 10.The olefin-based polymer of claim 9, wherein the carrier includes atleast one selected from the group consisting of silica, alumina, andmagnesia.
 11. The olefin-based polymer of claim 9, wherein a totalamount of the hybrid transition metal compound supported on the carrieris 0.001 to 1 mmol based on 1 g of the carrier, and a total amount ofthe cocatalyst compound supported on the carrier is 2 to 15 mmol basedon 1 g of the carrier.
 12. The olefin-based polymer of claim 3, whereinthe olefin-based polymer is a copolymer of the olefin-based monomer andan olefin-based comonomer.
 13. The olefin-based polymer of claim 12,wherein the olefin-based monomer is ethylene, and the olefin-basedcomonomer is one or more selected from the group consisting ofpropylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene,1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, and1-hexadecene.
 14. The olefin-based polymer of claim 13, wherein theolefin-based polymer is a linear low-density polyethylene in which theolefin-based monomer is ethylene and the olefin-based comonomer is1-hexene.
 15. A method for preparing an olefin-based polymer, the methodcomprising: polymerizing an olefin-based monomer in the presence of ahybrid catalyst including: at least one first transition metal compoundrepresented by the following Chemical Formula 1; and at least one secondtransition metal compound selected from a compound represented by thefollowing Chemical Formula 2 and a compound represented by the followingChemical Formula 3, thereby obtaining an olefin-based polymer, whereinthe olefin-based polymer has (1) a density of 0.915 to 0.935 g/cm³; (2)a melt index (I_(2.16)) of 0.3 to 3.0 g/10 min as measured with a loadof 2.16 kg at 190° C.; (3) a ratio between a melt index (I_(21.6))measured with a load of 21.6 kg and a melt index (I_(2.16)) measuredwith a load of 2.16 kg at 190° C. (melt flow ratio; MFR) of 20 to 50;and (4) a comonomer distribution slope (CDS) defined by the followingEquation 1 of 3 or more, and a film prepared therefrom has a drop impactstrength of 1,200 to 1,550 g based on a thickness of 50 μm:

$\begin{matrix}{{CDS} = \frac{{\log C_{80}} - {\log C_{20}}}{{\log M_{80}} - {\log M_{20}}}} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$ wherein M₁, M₂, X, and R₁ to R₁₀ are as defined in claim3, and C₂₀, C₈₀, M₂₀, and M₈₀ are as defined in claim
 1. 16. The methodfor preparing an olefin-based polymer of claim 15, wherein thepolymerization of the olefin-based monomer is gas phase polymerization.